Various food preservation methods, starting with traditional salting and drying from ancient times, such as canning, retort, vacuum packing, low-temperature preservation, freezing, etc. have been made in the process of technological progression with change of the ages.
The important point of them is how to prevent rot by microbes and degeneration by chemical reaction. Especially, freezing method (freezing apparatus), currently in mainstream and developed to aim at preservation of fresh foods with original state (color, taste, flavor, feel, etc.), and long-term preservation of the state just after the production of processed foods, is deeply permeating into our eating habits not only in general households but restaurant industry.
Rapid freezing technology exists on the top of them. Different from simple slow freezing, for example, an air blast system to freeze articles (food or foodstuff) to be frozen by blowing cold air of very low temperature of −35° C. to −55° C., a brine system in which articles are made contact with liquid cooling media, and a compound system of the both (refer to patent document 1, for example).